A growing body of evidence suggests that an individual's social network may be an important determinant of health and well-being -- for example, socially isolated individuals appear to be a greater risk for cardiovascular disease. Preliminary evidence implicates excessive cardiovascular reactivity to psychological challenge as a potential risk factor for coronary artery disease and hypertension; effects of social processes on cardiovascular reactivity would provide a potential mechanism by which social network characteristics may reduce health risk. Recent laboratory studies show that social affiliation reduces the effects of psychological challenge on cardiovascular reactivity. The generalizability of these laboratory effects are examined in this study by exploring the impact of socially supportive interactions on cardiovascular responsiveness to significant behavioral challenges in the course of everyday living. Subjects will be monitored intermittently over the course of a week-long period, providing cardiovascular assessments as well as information about environmental stressors, social stressors, and socially supportive transactions. Time series regression analyses will be used to examine the effects of these psychosocial factors on eliciting a moderating ambulatory cardiovascular responsivity. This study, a unique integration of three established methodologies (ambulatory cardiovascular monitoring, experience sampling using computer diary techniques, and ambulatory social interaction assessment) will advance our understanding of one of the mechanisms by which social processes may alter cardiovascular disease risk.